1. Field of the Invention
The present invention relates to a robot controller which executes a preset operation content when it judges that a standard moving part installed on a robot reaches a preset setting position.
2. Description of the Related Art
FIG. 15 is a drawing showing a transfer operation of a workpiece 2 by a robot. The robot performs the operation in the order of (1) to (6) of FIG. 15, retains the workpiece 2 retained by a chuck 3 by a robot hand 1, and transfers the workpiece 2 to a predetermined place. A part of a program example of the related art in this case is shown in Table 1 indicated below. Further, FIG. 16 is a graph showing a change with time of the speed of the robot hand when the operation of the program shown in Table 1 is performed.
TABLE 1  :  :LMOVE#ALMOVE#BSIGNAL1, 2 (Hand opening instruction, chuckopening instruction)LMOVE#CSIGNAL−1 (Hand closing instruction)LMOVE#DLMOVE#ESIGNAL3 (Workpiece supply instruction)LMOVE#A  :
The robot controller moves the hand 1 toward the chuck 3 retaining the workpiece 2 and stops it at a first position A above the workpiece 2 (LMOVE #A). Next, the robot controller moves the hand 1 from the first position A to a second position B close to the chuck 3 and stops the hand 1 at the second position B (LMOVE #B). Next, the robot controller gives an instruction for opening the hand 1 and an instruction for opening the chuck 3 (SIGNAL 1, 2) and then moves the hand 1 from the second position B to a third position C close to the chuck 3 and stops the hand 1 at the third position C (LMOVE #C). Next, the robot controller gives an instruction for closing the hand 1 (SIGNAL-1) and moves the hand 1 from the third position #C to a fourth position D and stops the hand 1 at the fourth position D. When the hand 1 moves to the fourth position D, it enters a state of clamping the workpiece 2. Next, the robot controller moves the hand 1 to a fifth position E farther than the fourth position D (LMOVE #E) from the chuck 3 and stops the hand 1 at the fifth position. Next, the robot controller gives an instruction for supplying another workpiece 2 to the chuck 3 (SIGNAL 3) and moves the hand 1 from the fourth position E to the first position A.
As mentioned above, the robot hand controller, when the hand 1 reaches the predetermined setting positions B, C, and E, stops the robot, opens or closes the hand 1, outputs the chuck opening or closing instruction, and outputs the workpiece supply instruction.
Further, a controller disclosed in Japanese Patent Laid-Open Publication No. 9-258812 outputs a setting position passing signal when it judges that an estimated position of a laser welding device reaches a predetermined setting position during the laser welding device is moved by a robot along a predetermined movement path. The controller decides the estimated position on the basis of the change in the movement instruction of the laser welding device and the movement position.
Further, the controller disclosed in Japanese Patent Laid-Open Publication No. 58-177289 moves a hand horizontally and vertically by a robot and handles a workpiece. The controller moves the hand horizontally, judges that it reaches a setting position before a handling position, and outputs a setting position passing signal. And, when the controller outputs the setting position passing signal, it starts the vertical movement of the hand. By doing this, the hand draws a smooth arc movement trace and reaches the handling position.
As mentioned above, the robot controller of the related art executes operation contents in accordance with the setting position when judging that a standard moving part, such as a robot hand, installed on the robot reaches a predetermined setting position on the movement route,
In the related art shown in FIG. 16, the controller, when the hand 1 reaches the setting positions B, C, and E on the movement route, stops the movement of the hand 1. Therefore, whenever the hand 1 moves to the setting positions B, C, and E, the movement operation of the hand 1 is discontinued, and the mean speed of the hand 1 is lowered, and a problem arises that the operation efficiency is lowered.
FIG. 17 is a drawing for explaining the movement route of the standard moving part and FIG. 18 includes graphs showing a change with time of the moving speed of the standard moving part. FIG. 18(1) shows a case that a first operation D1 moving from the movement start position A to the setting position C and a second operation D2 moving from the setting position C to the movement end position B are performed individually and FIG. 18(2) shows a case that a part of the first operation D1 and a part of the second operation D2 are performed simultaneously.
As shown in FIG. 17, even if the standard moving part is moved from the movement start position A to the movement end position B, it may be shifted from a movement route 18 for direct movement from the movement start position A to the movement end position B, thus the setting position C may be set. In this case, the standard moving part moves from the movement start position A toward the setting position C and stops at the setting position C. And, during movement from the setting position C toward the movement end position B, the robot controller executes the operation contents in accordance with the setting position C.
In this case, one single operation D3 directly moving from the movement start position A to the movement end position B as shown by the dashed line in FIG. 18(1) is divided into the first operation D1 moving from the movement start position A to the setting position C and the second operation D2 moving from the setting position C to the movement end position B. Therefore, to move toward the setting position C halfway the movement from the movement start position A to the movement end position B, the hand must slow down and the time W1 required for movement from the movement start position A to the movement end position B becomes longer than the time W2 required for direct movement from the movement start position A to the movement end position B.
Further, when the setting position C is installed at a place shifted from the transfer route 18 for direct movement from the movement start position A to the movement end position B, the movement route of the standard moving part is extended, thus the movement time becomes much longer than direct movement from the transfer start position A to the transfer end position B.
In the art disclosed in Japanese Patent Laid-Open Publication No. 58-177289, as shown in FIG. 18(2), the standard moving part, before completion of the first operation D1, starts the second operation D2 together with the first operation D1. In this case, as shown by a two-dot chain line in FIG. 17, the standard moving part does not pass through the setting position C but moves in the neighborhood of the setting position C along a smooth track 17, and moves from the movement start position A to the movement end position B. And, the standard moving part, at the point of time tC when the second operation is started together with the first operation D1, executes the operation contents according to the setting position C. Even in this case, as compared with the single operation D3, during the period W3 when the first operation D1 and the second operation D2 are performed at the same time and the periods W4 and W5 before and after it, the speed of the standard moving part is inevitably lowered. Therefore, the time W6 required for movement from the movement start position A to the movement end position B becomes longer than the time W2 required for direct movement from the movement start position A to the movement end position B.